I've been trying to find a simple sans serif font for a specialist mathematical programming language that uses special symbols (available in unicode fonts). Some unicode fonts have inconsistent symbols sizes eg Tahoma and Verdana, DejaVu sans has advanced logic symbols (the round ones) that are consistent in size but larger than all the other symbols.

These fonts render some or all of vertical bar, capital I small L and digit 1 identically. This is unacceptable in a programming language where a single wrong character can cause a bug that is very difficult to trace (the program will look right). Capital O and zero also need to be obviously different.